机架rack.input变量被截断？

Question

我写了一个 Rack Middleware 来自动解压压缩的请求体。该代码似乎工作得很好，但是当我将其插入我的 Rails 应用程序时，我从 ActionController::ParamsParser 收到失败“无效的 JSON”。

作为一种调试机制，我将压缩内容和解压缩内容写入文件（以确保代码正常工作），并且我确实收到了原始 JSON 文档（在客户端将其压缩之前）。

我发布的数据是 JSON 数据，解压缩的内容被检测为来自 http:// 的有效 JSON jsonlint.com。

有什么想法我做错了吗？

class CompressedRequests
  def initialize(app)
    @app = app
  end

  def call(env)
    input = env['rack.input'].read

    #output the zipped data we received
    File.open('/Users/ben/Desktop/data.gz', 'w+') do |f|
      f.write input
    end

    if env['REQUEST_METHOD'] =~ /(POST|PUT)/ 
      if env.keys.include? 'HTTP_CONTENT_ENCODING'
        new_input = decode(input, env['HTTP_CONTENT_ENCODING'])
        env['rack.input'] = StringIO.new(new_input)

        #output our decoded data (for debugging)
        File.open('/Users/ben/Desktop/data.txt', 'w+') do |f|
          f.write env['rack.input'].read
        end

        env.delete('HTTP_CONTENT_ENCODING')
      end
    end

    env['rack.input'].rewind
    status, headers, response = @app.call(env)
    return [status, headers, response]
  end

  def decode(input, content_encoding)
    if content_encoding == 'gzip'
      Zlib::GzipReader.new(input).read
    elsif content_encoding == 'deflate'
      Zlib::Inflate.new.inflate new input
    else
      input
    end
  end
end

这是我从控制台收到的错误：

Contents::"2010-05-17T12:46:30Z","background":false},{"longitude":-95.38620785000001,"latitude":29.62815358333334,"estimated_speed":14.04305,"timestamp":"2010-05-17T12:46:36Z","background":false},{"longitude":-95.3862767,"latitude":29.62926725,"estimated_speed":39.87791,"timestamp":"2010-05-17T12:46:42Z","background":false},{"longitude":-95.38655023333334,"latitude":29.63051011666666,"estimated_speed":46.09239,"timestamp":"2010-05-17T12:46:49Z","background":false},{"longitude":-95.38676226666666,"latitude":29.63158775,"estimated_speed":47.34936,"timestamp":"2010-05-17T12:46:55Z","background":false},{"longitude":-95.38675346666666,"latitude":29.63219841666666,"estimated_speed":22.54016,"timestamp":"2010-05-17T12:47:03Z","background":false},{"longitude":-95.38675491666666,"latitude":29.63265714999999,"estimated_speed":14.03642,"timestamp":"2010-05-17T12:47:10Z","background":false},{"longitude":-95.38677551666666,"latitude":29.63358661666667,"estimated_speed":29.29489,"timestamp":"2010-05-17T12:47:17Z","background":false},{"longitude":-95.38679026666662,"latitude":29.63466445,"estimated_speed":38.34926,"timestamp":"2010-05-17T12:47:24Z","background":false},{"longitude":-95.38681656666668,"latitude":29.63590941666666,"estimated_speed":44.82093,"timestamp":"2010-05-17T12:47:31Z","background":false},{"longitude":-95.38683366666667,"latitude":29.63679638333334,"estimated_speed":40.21729,"timestamp":"2010-05-17T12:47:37Z","background":false},{"longitude":-95.38685133333333,"latitude":29.63815714999999,"estimated_speed":44.86543,"timestamp":"2010-05-17T12:47:44Z","background":false},{"longitude":-95.3868655
/!\ FAILSAFE /!\  Mon Oct 18 18:18:43 -0500 2010
  Status: 500 Internal Server Error
  Invalid JSON string
    /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/json/backends/yaml.rb:14:in `decode'
    /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/json/decoding.rb:11:in `__send__'
    /Library/Ruby/Gems/1.8/gems/activesupport-2.3.5/lib/active_support/json/decoding.rb:11:in `decode'
    /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/params_parser.rb:42:in `parse_formatted_parameters'
    /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/params_parser.rb:11:in `call'
    /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/cookie_store.rb:93:in `call'
    /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/failsafe.rb:26:in `call'
    /Users/ben/projects/safecell/safecellweb/lib/compressed_requests.rb:36:in `call'
    /Library/Ruby/Gems/1.8/gems/rack-1.0.1/lib/rack/lock.rb:11:in `call'
    /Library/Ruby/Gems/1.8/gems/rack-1.0.1/lib/rack/lock.rb:11:in `synchronize'
    /Library/Ruby/Gems/1.8/gems/rack-1.0.1/lib/rack/lock.rb:11:in `call'
    /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:114:in `call'
    /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/reloader.rb:34:in `run'
    /Library/Ruby/Gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:108:in `call'
    /Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/rails/rack/static.rb:31:in `call'
    /Library/Ruby/Gems/1.8/gems/rack-1.0.1/lib/rack/urlmap.rb:46:in `call'
    /Library/Ruby/Gems/1.8/gems/rack-1.0.1/lib/rack/urlmap.rb:40:in `each'
    /Library/Ruby/Gems/1.8/gems/rack-1.0.1/lib/rack/urlmap.rb:40:in `call'
    /Library/Ruby/Gems/1.8/gems/rails-2.3.5/lib/rails/rack/log_tailer.rb:17:in `call'
    /Library/Ruby/Gems/1.8/gems/rack-1.0.1/lib/rack/content_length.rb:13:in `call'
    /Library/Ruby/Gems/1.8/gems/rack-1.0.1/lib/rack/handler/webrick.rb:50:in `service'

最后一条信息，我在 ActionController::Failsafe 之后插入此中间件。

编辑：看起来这不是截断问题

经过更多挖掘，看起来这毕竟不是截断问题。日志只是对输出进行了剪辑，因此看起来像是截断问题。

此时我不确定为什么 JSON 无效。我需要手动转义吗？

Answer 1

无论如何，我都不是红宝石专家。我也没有尝试重现这个问题来验证我的结果。但在深入研究了机架和动作包代码之后，我可能会有一些东西。

“rack.input”的文档指出：
“输入流是一个类似 IO 的对象，其中包含原始 HTTP POST 数据。”

所以你似乎正确地使用了它。

但是，actionpack 尝试从正文中解析 JSON（如果内容类型指定为 JSON）并像这样检索正文：

when :json
    body = request.raw_post

其中“request”是 actionpack 自己的 Request 类，“raw_post”定义如下：

def raw_post
  unless @env.include? 'RAW_POST_DATA'
    @env['RAW_POST_DATA'] = body.read(@env['CONTENT_LENGTH'].to_i)
    body.rewind if body.respond_to?(:rewind)
  end
  @env['RAW_POST_DATA']
end

和“Request” .body”是：

def body
  if raw_post = @env['RAW_POST_DATA']
    raw_post.force_encoding(Encoding::BINARY) if raw_post.respond_to?(:force_encoding)
    StringIO.new(raw_post)
  else
    @env['rack.input']
  end
end

一切看起来都很好（尽管弄清楚谁先缓存该值很令人困惑:)）。
看起来问题在于如何读取帖子数据：

@env['RAW_POST_DATA'] = body.read(@env['CONTENT_LENGTH'].to_i)

所以我猜问题是，由于您更改了“rack.input”但不更新“CONTENT_LENGTH”，actionpack 正在截断数据，因为显然是压缩内容会比解压后的内容短。

尝试更新中间件代码中的“CONTENT_LENGTH”，看看是否可以解决问题。